1. Technical Field
The present invention generally relates to a motor unit including a spindle motor and a recording-disk-driving device including the same, and in particular relates to a spindle motor in which the electric conductivity needs to be secured between components of the spindle motor.
2. Description of the Related Art
Electrostatic discharge (ESD), in which static electricity damages a magnetic head of a recording-disk-driving device, is one of the main causes of the crashes of recording-disk-driving devices such as hard disk drives (HDDs). For example, the static electricity is charged to the HDD by the friction between the spindle motor and the recording disk on assembling the HDD or by the friction between the air and the recording disk during the rotation thereof. When the static electricity is discharged to the magnetic head, which is sensitive to static electricity, the magnetic head is damaged. In order to prevent ESD, an electroconductive adhesive may be applied between the components so that each component is conductive with the housing of the HDD. With such configuration, the static electricity is not charged to HDD.
However, it is necessary to put the spindle motor assembled with the electroconductive adhesive in the thermostatic chamber held 60 to 90° C. for predetermined time to harden the adhesive. It requires a lot of time for hardening the adhesive and investments on equipments to manufacture such spindle motors.